// http://www.paulund.co.uk/include-all-custom-post-types-in-wordpress-search
function mysite_include_post_types_in_search($query) {
  if(is_search()) {
    $post_types = get_post_types(array('public' => true, 'exclude_from_search' => false), 'objects');
    $searchable_types = array('nav_menu_item');
    if($post_types) {
      foreach( $post_types as $type) {
        $searchable_types[] = $type->name;
      }
    }
    $query->set('post_type', $searchable_types);
  }
  return $query;
}

add_action('pre_get_posts', 'mysite_include_post_types_in_search');